1. Field of the Invention
The invention relates to a measuring device for detecting a relative movement between at least one magnetic field sensor array, integrated into a semiconductor chip, and a transmitter for said sensor array, whereby the transmitter and the sensor array are penetrated by the magnetic flux of a magnet and the transmitter has teeth, which can be moved past the sensor array during the relative movement, or whereby the transmitter has magnetic poles, which can be moved past the sensor array during the relative movement, whereby the sensor array has a differential magnetic field sensor, which has a first measuring plate and a second measuring plate, which are offset relative to one another in the direction of the relative movement.
2. Description of the Background Art
EP 1 182 461 A2, which corresponds to U.S. Pat. No. 6,545,462, discloses a measuring device of this type, which has a disk-shaped transmitter with magnetic poles, which move past the magnetic field sensor during a rotation movement of the transmitter around an axis arranged at right angles to the plane of the disk. The magnetic field sensor has three differential magnetic field sensors which are integrated into a semiconductor chip and each of which has two horizontal measuring plates, which are arranged at a distance of 120° on a circular path concentric to the transmitter's axis of rotation. A disk-shaped layer of a magnetically conductive material, which acts as a magnetic field concentrator and covers the measuring plates, is arranged on the semiconductor chip. In a measuring device in which the distance between the two measuring plates of the differential magnetic field sensor in the direction of the relative movement is small relative to the distance of the magnetic pole, only a correspondingly small differential measuring signal results. At large relative velocities between the transmitter and semiconductor chip, the differential measuring signal can be evaluated relatively well in order to determine, e.g., the relative position between the transmitter and semiconductor chip. At small relative velocities and particularly when the differential magnetic field sensor is arranged centered between two magnetic poles of the transmitter, the evaluation of the differential measuring signal is difficult, however.
EP 1 182 461 A2 discloses further a measuring device, which has two differential magnetic field sensors which are integrated into a semiconductor chip and each of which comprises two horizontal measuring plates, which are arranged at a distance of 180° on a circular path concentric to the transmitter's axis of rotation. In addition, a magnetic field sensor element with another horizontal measuring plate, which is arranged centrally to the circular path, is provided in the semiconductor chip. The absolute value of the magnetic field in the center of the circle can in fact be measured with the aid of this sensor element. The sensor element, however, is not suitable for detecting the relative position of the teeth or magnetic poles of a transmitter arranged concentrically to the circular path. Thus, only differential measuring signals are available here as well for determining the rotational position of the teeth or magnetic poles of the transmitter.
DE 10 2004 017 191 A1, which corresponds to U.S. Pat. No. 7,535,215, discloses a measuring device, which has a first differential magnetic field sensor which is integrated into a semiconductor chip and has two magnetic field sensors of the same type, each of which detects a horizontal magnetic field component. The distance of the first magnetic field sensors corresponds to the pitch length of the pole wheel. In addition, the semiconductor chip has a second differential magnetic field sensor, which has two magnetic field detection devices, whose spacing also corresponds to the pitch length and each of which is arranged above or below a magnetic field sensor assigned to it. The differential measuring signal of the first differential magnetic field sensor is used as a rotary speed signal. A direction signal is generated from the differential measuring signals of the two differential magnetic field sensors. The measuring device, however, has a relatively complicated structure.